568 Records of the Indian Museum. [Vol. XXII, 



viduals be examined, and due attention paid to the protoconch, 

 form the most satisfactory basis for specific identification among 

 the Indian species, among which conspicuous anatomical differ- 

 ences such as Baker ' discovered in the North American Limnaeidae 

 do not exist. Anatomical differences of course there are, but they 

 are so minute, so difficult to find and above all so inconstant that 

 they are of little use in taxonomy. 



The radular teeth in all the Indian, Persian and Mesopotamian 

 species we have examined conform to a type somewhat different 

 from that described for any European species, differing in detail 

 in the different forms, but vary greatly not only in accord with 

 race and locality but also with individual idiosyncracy, while small 

 specific differences in the genitalia are liable to be obscured by the 

 state of sexual activity, especially by protandry. 



In the anatomy of the radula and genitalia the Indian 

 Limnaeidae (omitting the Palaearctic Himalayan species) differ 

 little from those referred by Baker to the Holarctic genus or 

 subgenus Galba, Schrank, but the shell does not quite conform to 

 this type. It is, indeed, of more than one type and Limnaea acu- 

 minata stands out very distinct in shell-characters from its con- 

 geners and is more like Galba than the other species in our fauna. 



Limnaea acuminata, Lamarck. 

 (Plate VII, figs. 1—3.) 



1878. Litnnaeits acuminatus, Nevill, Hand List Moll. Ind. Afiis., p. 



-33- 

 1881. Limnaea aciimmala, von Martens, Conch. Mitfli. I, p- 75. pi- 



xiv. 

 1915. Limnaea acuminata (in part), Preston, Faun. Brit. Ind. Fresliw.- 



MolL, p. 106. 

 1919. Limnaea acuminata (with var. nana), L. amygdaliim and ( .' 1 L. 



chlamvs. Annandale and Prashad, /?ec. Ind. Mus. XVI, pp. 



140-142, hg-s. 3, 4, pi. iv, tier. ], pi. V, figs. 1-3. 



Preston, in the Fauna of British India has distributed the forms 

 of Limnaea indiscriminately into subgenera and species and several 

 of those he attributes to L. acuminata have, as von Martens had 

 shown previously, no resemblance to it. We include in it here all 

 the forms comprised in the species by Nevill and by von Martens, 

 with the possible exception of L. chlamys, Benson. Of all the In- 

 dian freshwater Gastropods L. acuminata is the most liable to 

 individual variability and it also exhibits considerable plasticity 

 in response to environment. It is not surprising, therefore, that 

 numerous names have been given to different "forms." Several 

 of these (patida, Troschel, rufescens, Gray, strigata, Hanley and 

 Theobald, gracilior, v. Martens) refer merely to shapes of shell 

 that may be assumed almost anywhere in the normal environ- 

 ment of the species, i.e. in a pool of perennial water pro- 

 vided with abundant aquatic vegetation of a succulent nature 



1 Spec. Pub. Chicago. Acad. Sci. Ill (1911). 



